Government plans to speed up assessment time for would-be adopters could lead to paedophiles slipping through the net, social workers have warned.

The British Association of Social Workers (BASW) said plans to speed up the time for potential adopters to be assessed could lead to safeguards that screen out child abusers being missed.

The body compared the potential crisis to those in the Catholic Church and the alleged abuse by BBC presenter Jimmy Savile.

Its concerns come after new figures shone the spotlight on the adoption system last week, revealing that children in England are left in care for nearly 21 months on average before being adopted.

According to the adoption scorecards published by the Department for Education (DfE), more councils in England are now failing to meet the Government's threshold on how long a child should wait between being taken into care and moving in with their new adoptive parents.

The scorecards' publication is part of a Government action plan to reform the adoption system, including proposals to speed up the assessment of potential adopters, cutting the time they wait to be approved to six months. But the BASW warned that this could lead to vital safeguards to screen out paedophiles being missed.

The organisation said child protection social workers described working extra hours to deal with the sheer volume of cases akin to "the M25 at rush hour" and demanding more speed with fewer resources would lead to paedophiles flourishing.

BASW member Judith Acreman, herself an adoptive parent, said: "One of the things that mustn't be forgotten when we're doing the 'quicker, faster, better' adoption assessments is that there is a really important safeguarding aspect to this work. Unfortunately, paedophiles will always locate the places where they are not scrutinised. And if we take the scrutiny level out of adoption then I'm very worried that it will become the latest example of the abuse we saw in children's homes, priests in the Catholic Church and by Jimmy Savile."

Minister for Children and Families, Edward Timpson, said: "These suggestions are crass and irresponsible. Clearly, a child's safety is paramount in adoption decisions. However, it is simply unacceptable that, on average, the process takes almost two years. More than 4,000 children in care are still waiting to be adopted.

"Children in care deserve a more effective system, with the same rigorous safeguards, that will place them in a loving and stable family sooner. That is what we want and that is surely something every social worker supports."